Buick Riviera

Don't expect the Buick marque to suddenly crop up in parent company General Motors' UK showrooms anytime soon, but the Riviera concept car is still significant.

Already seen at the 2007 Shanghai motor show, the Riviera takes its name from luxury coupes developed by Buick from 1963 until 1999.

Its significance lies in its hybrid powertrain, which GM says it will sell on production models in the near future as part of its push to cut emissions.

There's no clearer indication of how serious America is getting about its push to cut emissions - and, just as importantly, there's no clearer message that even the high-end brands are not immune.